1. Field of the Invention
This invention relates to a disposable blood collection device employing a double-ended cannula which is attached to the device preferably immediately prior to use, locked in an extended position for use, and retracted entirely within the barrel to a permanently locked position after use to protect against accidental needle sticks.
Medical devices using needles which are retained in a retracted position after the needle is used to guard against accidental sticks are well known. Such devices are shown, for example, in U.S. Pat. Nos. 4,650,468; 4,675,005; 4,692,156; and 4,507,117. Devices shown in the aforementioned patents are generally of the hypodermic syringe type, that is, a single needle point normally fixed to the end of a barrel and covered by a protective guard is utilized to inject fluids into or extract fluids from the human body. The needle point is retracted into the syringe barrel and retained therein by various means after use.
A somewhat different type of device has come into use with respect to the collection of blood samples. The device includes a double-ended cannula or needle, again is fixed to one end of the barrel and covered by a protective guard prior to use. The guard is removed and the end of the needle so uncovered is inserted into the patient's vein. A sterile evacuated container is applied to the other end within the barrel so that the pressure differential resulting thereby causes blood to be drawn from the vein into the evacuated container. When the container is filled, it is removed from the needle, thereby providing a sealed blood sample in the container. Examples of this type of device are shown in FIGS. 4-6 of U.S. Pat. No. 4,592,744 and in FIGS. 1-3 of U.S. Pat. No. 4,643,199. In each of these devices, a double-ended cannula is normally fixed to the end of the barrel so that one end extends from the barrel and is covered by a protective guard prior to use. After use, the double ended cannula is retracted within the barrel so as to be disposable without the danger of sticking personnel thereafter handling it. However, both of these devices require the user to use both hands in order to retract the needle after use, and thus are relatively complicated and time consuming in use. In addition, having the patient-inserted end of the cannula normally fixed to the end of the barrel takes up additional shipping space and requires removal of the guard prior to use.
A blood collection device having a double-ended cannula disposed in a barrel, open at one end to permit the insertion of an evacuated sample collection container therein onto one end of the double-ended cannula, and an aperture at the other barrel end to permit the extension and retraction therethrough of the other end of the double-ended cannula is shown in U.S. Pat. No. 4,774,964, entitled Blood Collection Device, issued Oct. 4, 1988, Jean A. Bonaldo, Inventor. This device has a first disc disposed within the barrel to which the double-ended cannula is fixed so as to extend to each side thereof and be axially aligned within the barrel in a shipping position in which the cannula is completely contained within the barrel prior to use. A second disc, disposed within the barrel between the first disc and the barrel open end, has an aperture axially formed therein so as to permit one end of the cannula to pass therethrough. The first disc and the second disc are connected together by flexible connectors within the barrel to permit preselected relative movement therebetween. When the second disc is moved toward the barrel closed end, the first disc is moved against the barrel closed end, so that the cannula extends out of the barrel aperture When the second disk is thereafter moved in the opposite direction, the first disc is withdrawn by the connectors from the barrel closed end in a spaced-apart relationship from the second disc to a position in which both ends of the cannula are disposed within the barrel. Locking means for locking the first disc and second disc within the barrel in this spaced-apart relationship and manual operating means operable for initiating the movement of said discs to said spaced-apart relationship in conjunction with said connectors are provided. However, this design is comparatively expensive to manufacture and assemble, by reason of the portions of its structure which use two discs connected together by the flexible connectors.
U.S. Pat. No. 4,900,310 describes a blood collection device housing a cylindrical sheath open at one end and partially closed at the other end with a closed longitudinal slot formed in the sheath. A piston, disposed in the sheath so as to be slidable between a cannula-extended position and a cannula retracted position, has a threaded axial bore adapted to receive a complementary threaded boss on a cannula so the cannula extends longitudinally through the piston bore with one end of the cannula in the sheath and the other end of the cannula extending through the partially closed end of the sheath when the piston is in the extended position. A radially extending actuator pin formed on the piston extends through the longitudinal slot so as to be manipulable with one hand to move the piston from the extended position to the retracted position to enclose the cannula within the sheath. The longitudinal slot may have suitable detent means at one or both ends to provide that the piston be lightly held in the extended position and locked in the retracted position. However, because the piston is only lightly held in the extended position, when the cannula is screwed into the piston, a possibility exists that excess force will cause the piston to retract, necessitating holding the piston in place by the actuator pin.